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Discussion Starter #1
Long story short. have a truck with a busted stock ignition switch and want to install a panel mounted universal switch.

Truck in question is a 95 Chevy P30 Step-up Van food truck.

Schematic below plus what I am proposing. Any electrical guys see why it wouldnt work?



 

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Appears correct to me.
The only thing not completely clear on the original schematic is that the battery (not that aux battery depicted in the upper-right corner) is not shown on this diagram.

But it seems clear that the RED wire(s) from BATT 1 and BATT 2 terminals on the original switch are the main battery positive.

Nice adaptation for posting purposes!
Of course you're gonna connect the wires from your new switch to the wires on the schematic running from the original switch into the remainder of the circuit, not to the terminals of the original switch (as you've sketched it here), yeah?
 

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Discussion Starter #3 (Edited)
Appears correct to me.
The only thing not completely clear on the original schematic is that the battery (not that aux battery depicted in the upper-right corner) is not shown on this diagram.

But it seems clear that the RED wire(s) from BATT 1 and BATT 2 terminals on the original switch are the main battery positive.

Nice adaptation for posting purposes!
Of course you're gonna connect the wires from your new switch to the wires on the schematic running from the original switch into the remainder of the circuit, not to the terminals of the original switch (as you've sketched it here), yeah?

Thanks for the reply. Batt 1, 2 and 3 go to a junction block which comes from the battery + terminal. Pink serves no function so I left it out.

Planning on unplugging the column mounted switch connector pigtails and use some spade connectors to send the signals to the ring terminals on the universal switch. This is what the switch looks like.

 

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Gotta love those old-fashioned automotive schematics!
That damn diagram (the original schematic, not your sketch) is clear as mud.

That's one thing the German auto makers got right years ago, and the U.S. auto makers gradually adapted/adopted... a more formally organized, more modular style.
The German auto makers adapted that from the way German companies draw their industrial equipment electrical schematics..

In that original schematic you posted, the thing that makes it a mess (the thing that took the U.S. makers years to learn and that they learned from the Germans) is that you do not want to organize the schematic to mimic the physical arrangement of the (electrical) parts of the car...


In this particular diagram, they arranged it around the relative layout of the fuse-holders.
Then they began drawing in all the wires around that.
Makes for a non-intuitive, crowded, jumbled schematic depiction of the circuit.

The alternative is to name the fuses (like FU-1, FU-2 or similar) and draw the schematic to depict the scheme (root word of "schematic") of the circuit.

Then, include a layout diagram as needed to show where/how those fuses are physically arranged, to help the owner or mechanic locate and identify them (like the location diagram on the underside of your 355 fusebox lid). That is to say, depict physical location/physical arrangement on separate diagrams, not on the schematic.


The schematic though..... the layout and organization of the schematic should be driven by the (electrical) functionality, and not the physical arrangement.

Case in point.... on that diagram the accessories fuse is adjacent to the instrument-lamps fuse and above the hazard-lights fuse.... but those circuits have nothing at all to do with each other.



**** ETA: Not my place to say really, but since this pertains to a non 355 vehicle, it should probably be moved to the Off-Topic forums. ***


.
 

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Discussion Starter #5
Cool. I thnk I am going to roll with this. The universal switch is like $25 plus I have wires and spade connectors. Hopefully I dont fry anything.
 

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Discussion Starter #6
OK. if I can get some help with this here since Im even more confused now. Im going off a schematic for a 88 model when I have a 95 and cant find the one I need.


First pic below shows my wire colors.

Second pic below shows the reference at the oem switch

Instead of pink for ignition I have white which doesnt show any connection on the diagram. Do I need to connect that white to 12V so the distributor has power or is that white a Tach signal?

I suppose i can bring my laptop and a USB scope I have to see which wire is the tach signal







 

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atxjax-

If I can help I'm happy to.
I'm only checking in here 'cause I'm at work.
(and the browser I have here at my desk is like two generations old and your pics show as a red x)

I'll need to take a look later tonight.
Perhaps someone else here wants to jump in on it, but if not then I'm more than happy to give it a look later.
 

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okay cowboy, here's what I have..
(sorry, I'm not where I can do any sketches, but I'm confident we can do this anyway..)

The complication here for purpose of discussion is that your late 70's switch diagram doesn't identify any of the terminals with a number or anything of the sort... only by description and wire-color.

So let's do it this way-
You have the original wires in the truck that presently connect to the existing switch, and you have the replacement switch.
So, I'm going to list the existing wires (that you need to connect) on the LEFT, and the replacement switch on the RIGHT in the following list..
[Function: WIRE IN YOUR TRUCK] ---> [Terminal on Replacement switch]

------------------------------------------------------------------------------------
[Batt 1 and Batt 2 and Batt 3: Red] ---> [Battery]

[Ign1: pink and Ign3: orange] ---> [Ignition]

[Sol: yellow and purple] ---> [Solenoid]

[ACC: Brown] ---> [Accessory]

[Gnd1: Tan/white] ---> [Ground]

[Gnd2: dark green] ---> [Ground 2]
----------------------------------------------------------------------------

Notice: there seems to be some confusion about Gnd1 and Gnd2..
If the info I googled is correct, these circuits are only to flash the ALT and some other warning bulbs on the instrument cluster to test the bulbs.. with older vehicles you needed to light those warning-lamps on startup to alert you if the bulb was burned-out so you would know..

On the diagram of your truck wiring they are assigned "ground 1" and "ground 2" in what appears to me to be opposite the terminal identity of the terminals on the replacement switch you posted.
You may need to swap those two wires, I can't be sure. I seriously doubt it can hurt anything though.

What I believe is that it will not make any difference, as long as the dark green wire is connected to one of the Ground terminals on the switch, and the tan/white wire is connected to the other Ground terminals.

That is to say, I'm pretty certain that you'll find that both those contacts on the switch do the same thing. There are two of the Ground terminals (and two separate switch contacts inside the keyswitch) only because they needed to keep the circuit(s) to the two warning lamps on the cluster separate when the vehicle is running. (those two Ground terminals are both "on" only when the switch is held in the START position)



Problem is, I don't have your truck or the replacement switch here to check it out with a multimeter..


ETA: This morning looking at your diagram and my post of last night I noticed I had left out the ACC circuit: brown wire, so I added that.
Hope this helps!
 

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Discussion Starter #9 (Edited)
okay cowboy, here's what I have..
(sorry, I'm not where I can do any sketches, but I'm confident we can do this anyway..)

The complication here for purpose of discussion is that your late 70's switch diagram doesn't identify any of the terminals with a number or anything of the sort... only by description and wire-color.

So let's do it this way-
You have the original wires in the truck that presently connect to the existing switch, and you have the replacement switch.
So, I'm going to list the existing wires (that you need to connect) on the LEFT, and the replacement switch on the RIGHT in the following list..
[Function: WIRE IN YOUR TRUCK] ---> [Terminal on Replacement switch]

------------------------------------------------------------------------------------
[Batt 1 and Batt 2 and Batt 3: Red] ---> [Battery]

[Ign1: pink and Ign3: orange] ---> [Ignition]

[Sol: yellow and purple] ---> [Solenoid]

[ACC: Brown] ---> [Accessory]

[Gnd1: Tan/white] ---> [Ground]

[Gnd2: dark green] ---> [Ground 2]
----------------------------------------------------------------------------

Notice: there seems to be some confusion about Gnd1 and Gnd2..
If the info I googled is correct, these circuits are only to flash the ALT and some other warning bulbs on the instrument cluster to test the bulbs.. with older vehicles you needed to light those warning-lamps on startup to alert you if the bulb was burned-out so you would know..

On the diagram of your truck wiring they are assigned "ground 1" and "ground 2" in what appears to me to be opposite the terminal identity of the terminals on the replacement switch you posted.
You may need to swap those two wires, I can't be sure. I seriously doubt it can hurt anything though.

What I believe is that it will not make any difference, as long as the dark green wire is connected to one of the Ground terminals on the switch, and the tan/white wire is connected to the other Ground terminals.

That is to say, I'm pretty certain that you'll find that both those contacts on the switch do the same thing. There are two of the Ground terminals (and two separate switch contacts inside the keyswitch) only because they needed to keep the circuit(s) to the two warning lamps on the cluster separate when the vehicle is running. (those two Ground terminals are both "on" only when the switch is held in the START position)



Problem is, I don't have your truck or the replacement switch here to check it out with a multimeter..


ETA: This morning looking at your diagram and my post of last night I noticed I had left out the ACC circuit: brown wire, so I added that.
Hope this helps!

Thanks for the insight. Im thinking along the same line as you. Being that the OEM switch has Ign1 pink and ignition 3 orange , I wonder if that will cause an issue. I looked at where ignition 1 feeds to and its to the primary side of the distributor coil.

I am thinking about putting Ign 1 on a separate latching relay powered directly from the battery to avoid any issues. below is the schematic showing where the pink feeds into the coil primary.

Need to figure out how to run the Ign1 off a relay

 

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Thanks for the insight. Im thinking along the same line as you. Being that the OEM switch has Ign1 pink and ignition 3 orange , I wonder if that will cause an issue. I looked at where ignition 1 feeds to and its to the primary side of the distributor coil.
..

I'm thinking it will not be a problem.
On the original schematic, notice on the switch those black dots.
Those describe in which position of the switch (OFF, Accessory, Start, and Run) that contact will be "on". IGN 2 shows that the contact will be on in both positions Start and Run, which is typical for the actual ignition circuit. Gotta energize the coil to enable it to start up and run.

IGN 1 (pink) though, doesn't have those dots.
If you follow the pink wire though, it feeds the gauges, the turn-signals, that sort of stuff that you want on when the truck is started-up and running.

Again, the only ambiguous part about it is the abcense of those dots on the switch for IGN 1, but the electrical loads on that circuit tell the story.

The relay wouldn't hurt, only because you don't know what is the current capacity of the ignition-switch contacts on the replacement switch. The relay would remove the load of the turn-signals, etc from the switch.

That being the case, I would connect the relay coil to the IGN contact on the switch, same as the orange wire.
 

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Discussion Starter #11
I'm thinking it will not be a problem.
On the original schematic, notice on the switch those black dots.
Those describe in which position of the switch (OFF, Accessory, Start, and Run) that contact will be "on". IGN 2 shows that the contact will be on in both positions Start and Run, which is typical for the actual ignition circuit. Gotta energize the coil to enable it to start up and run.

IGN 1 (pink) though, doesn't have those dots.
If you follow the pink wire though, it feeds the gauges, the turn-signals, that sort of stuff that you want on when the truck is started-up and running.

Again, the only ambiguous part about it is the abcense of those dots on the switch for IGN 1, but the electrical loads on that circuit tell the story.

The relay wouldn't hurt, only because you don't know what is the current capacity of the ignition-switch contacts on the replacement switch. The relay would remove the load of the turn-signals, etc from the switch.

That being the case, I would connect the relay coil to the IGN contact on the switch, same as the orange wire.

Thanks man. Im weighing my options. Im gonna have to go out there to the truck and test each individual wire first before I buy the switch,
 
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